In order to enhance a rigidity of the side wall part of a tire, particularly of a run flat tire, a side reinforcing layer using a rubber composition alone or a composite of a rubber composition, a fiber, and the like, has been conventionally arranged.
For example, in order to secure the run flat durability of the run flat tire without damage to the rolling resistance in normal running, a tire having a side reinforcing rubber layer and/or a bead filler using a rubber composition containing a mixture of a rubber component, 55 parts by mass or more of carbon black based on 100 parts by mass of the rubber component, a phenol resin and a methylene donor (refer to PTL1).
In PTL2, a pneumatic radial tire is proposed, in which a PET with low thermal shrinkage is used as a carcass reinforcing material to reduce surface irregularities occurring at the roll-up end of the carcass in a side portion, thereby achieving weight reduction and improved productivity of the tire.
However, along with improvement in performance of automobiles, particularly of passenger cars, further improvement in the run flat durability is required.
Furthermore, it is also required to ensure to improve the side cut resistance of tires and the steering stability in normal running, together with the improvement in the run flat durability.